Cook the potatoes in boiling salted water for 10 minutes. Drain and set aside.
Meanwhile, prepare the vegetables.
Heat the oil in a large pan, add the onion and garlic and cook for about 5 minutes, stirring occasionally. Add the coconut and curry paste and cook, stirring, for 1 minute. Add the tomatoes and cook until mixture resembles a thick paste.
Add the vegetables, salt and 150ml water. Bring to the boil, cover and simmer for about 15 minutes, then add the spinach. Cook for a further 5 minutes or until all the vegetables are just tender. Season and add the coriander sprigs just before serving.